Pipelines¶

Before delving into the structure of the toast package, it is sometimes useful to look at (and use!) an example. One such program is the simple script below which simulates a fake satellite scanning strategy with a focalplane of detectors and then makes a map.

Simple Satellite Simulation¶

The current version of this tool simulates parameterized boresight pointing and then uses the given focalplane (loaded from a pickle file) to compute the detector pointing. Noise properties of each detector are used to simulate noise timestreams.

In order to create a focalplane file, you can do for example:

import pickle
import numpy as np

fake = {}
fake['quat'] = np.array([0.0, 0.0, 1.0, 0.0])
fake['fwhm'] = 30.0
fake['fknee'] = 0.05
fake['alpha'] = 1.0
fake['NET'] = 0.000060
fake['color'] = 'r'
fp = {}
fp['bore'] = fake

with open('fp_lb.pkl', 'wb') as p:
    pickle.dump(fp, p)

Note that until the older TOAST mapmaking tools are ported, this script requires the use of libmadam (the –madam option).

usage: toast_satellite_sim.py [-h] [--samplerate SAMPLERATE]
                              [--spinperiod SPINPERIOD]
                              [--spinangle SPINANGLE]
                              [--precperiod PRECPERIOD]
                              [--precangle PRECANGLE] [--hwprpm HWPRPM]
                              [--hwpstep HWPSTEP] [--hwpsteptime HWPSTEPTIME]
                              [--obs OBS] [--gap GAP] [--numobs NUMOBS]
                              [--obschunks OBSCHUNKS] [--outdir OUTDIR]
                              [--debug] [--nside NSIDE] [--baseline BASELINE]
                              [--noisefilter] [--madam] [--fp FP]

Simulate satellite boresight pointing and make a noise map.

optional arguments:
  -h, --help            show this help message and exit
  --samplerate SAMPLERATE
                        Detector sample rate (Hz)
  --spinperiod SPINPERIOD
                        The period (in minutes) of the rotation about the spin
                        axis
  --spinangle SPINANGLE
                        The opening angle (in degrees) of the boresight from
                        the spin axis
  --precperiod PRECPERIOD
                        The period (in minutes) of the rotation about the
                        precession axis
  --precangle PRECANGLE
                        The opening angle (in degrees) of the spin axis from
                        the precession axis
  --hwprpm HWPRPM       The rate (in RPM) of the HWP rotation
  --hwpstep HWPSTEP     For stepped HWP, the angle in degrees of each step
  --hwpsteptime HWPSTEPTIME
                        For stepped HWP, the the time in seconds between steps
  --obs OBS             Number of hours in one science observation
  --gap GAP             Cooler cycle time in hours between science obs
  --numobs NUMOBS       Number of complete observations
  --obschunks OBSCHUNKS
                        Number of chunks to subdivide each observation into
                        for data distribution
  --outdir OUTDIR       Output directory
  --debug               Write diagnostics
  --nside NSIDE         Healpix NSIDE
  --baseline BASELINE   Destriping baseline length (seconds)
  --noisefilter         Destripe with the noise filter enabled
  --madam               If specified, use libmadam for map-making
  --fp FP               Pickle file containing a dictionary of detector
                        properties. The keys of this dict are the detector
                        names, and each value is also a dictionary with keys
                        "quat" (4 element ndarray), "fwhm" (float, arcmin),
                        "fknee" (float, Hz), "alpha" (float), and "NET"
                        (float). For optional plotting, the key "color" can
                        specify a valid matplotlib color string.

Example: Proposed CoRE Satellite Boresight¶

Here is one example using this script to generate one day of scanning with a single boresight detector, and using one proposed scan strategy for a LiteCoRE satellite:

toast_satellite_sim.py --samplerate 175.86 --spinperiod 1.0 --spinangle 45.0
--precperiod 5760.0 --precangle 50.0 --hwprpm 0.0 --obs 23.0 --gap 1.0
--obschunks 24 --numobs 1 --nside 1024 --baseline 5.0 --madam --noisefilter
--fp fp_core.pkl --outdir out_core_nohwp_fast

Example: Proposed LiteBIRD Satellite Boresight¶

Here is how you could do a similar thing with a boresight detector and one proposed lightbird scanning strategy for a day:

toast_satellite_sim.py --samplerate 23.0 --spinperiod 10.0 --spinangle 30.0
--precperiod 93.0 --precangle 65.0 --hwprpm 88.0 --obs 23.0 --gap 1.0
--obschunks 24 --numobs 1 --nside 1024 --baseline 60.0 --madam --fp fp_lb.pkl
--debug --outdir out_lb_hwp

Creating Your Own Pipeline¶

TOAST is designed to give you tools to piece together your own data processing workflow. Here is a slightly modified version of the pipeline script above. This takes a boresight detector with 1/f noise properties, simulates a sort-of Planck scanning strategy, generates a noise timestream, and then generates a fake signal timestream and adds it to the noise. Then it uses madam to make a map.